1. Field of the Invention
The present invention relates to a cutting blade holding device of a veneer lathe for peeling a veneer from a log.
2. Description of the Prior Art
In a conventional veneer lathe, for example, as in a veneer lathe 1 shown in FIG. 7, spindles S, S for chucking a log W by end surfaces are rotatably mounted in a body frame F. On the body frame F, a blade stock 5 is mounted movably in a direction perpendicular to an axis L of the spindles S, S by means of transfer means D. On the surface facing the log W of the blade stock 5, a cutting blade B is mounted with its cutting edge located at the upper position in terms of rotational direction of the log W generally via a backing plate (not shown) (see U.S. Pat. No. 4,496,155). At upper positions in terms of the rotational direction of the log W and in terms of veneer traveling direction relative to the cutting blade B, nose bars are disposed. The blade stock 5 is moved toward the log W by actuating the transfer means D to press the cutting blade B against the peripheral surface of the rotating log W, whereby the log W is peeled into a veneer. The peeled veneer travels passing through between the nose bars N and the cutting blade B in the right upper direction in FIG. 7 and is delivered.
FIG. 6 is an explanatory view showing condition of attachment of a cutting blade B to on a blade stock 5 in another conventional veneer lathe. In the same manner as in the case shown in FIG. 7, to the rear surface (the surface facing the log W) of the blade stock 5 mounted movably in a direction perpendicular to an axis of spindles (not shown) which chuck a log W by end surfaces is fixedly applied a backing plate Bb with its bevel located at the upper position in terms of rotation of the log W (the upper course of a veneer traveling direction), and the cutting blade B held by a cutting blade holder Bc is pressed against the backing plate Bb by means of a blade presser, which is held by the blade stock 5 and oscillatory by a cylinder C, to hold the backing plate Bb between the blade stock 5 and the cutting blade B (see Japanese Utility Model Unexamined Publication No. 60606/1988).
The blade stock 5 and the backing plate Bb have such upper surfaces that, in their sections in the traveling direction of the shaved veneer V, the upper end portions thereof at the upper course of the traveling direction together form an acute-angular tip portion 51 and Bb1, and the upper surfaces constitute a continuous guide surface G downwardly slanting from the upper course to the lower course of the traveling direction of the veneer V. Along the guide surface G, the shaved veneer V is delivered.
The backing plate Bb and the blade stock 5 receive forces exerted on the cutting blade B during veneer peeling such as horizontal cutting resistance force in the direction departing from the log and toward the lower course of the veneer traveling direction to regulate deflection of the cutting blade B, thereby enabling a veneer to be shaved in a substantially uniform thickness.
However, there is undesired possibility that a tip portion of the cutting blade B is considerably deflected in the direction departing from the log W, according to angle condition of the cutting edge of the cutting blade B or at times of cutting knots, to cause breakage of the acute-angular tip portion K1 of the blade stock K. In particular, the blade stock K is as large in the direction perpendicular to the traveling direction of the veneer V as at least the axial length of the log W, and is thus made by casting to reduce production cost thereof. However, a casting is extremely susceptible to breakage by excessive force abruptly exerted thereon. Accordingly, an acute-angular tip portion K1 thereof is particularly likely to be damaged.
If a veneer V is peeled off with the acute-angular tip portion K1 of the blade stock K broken, the cutting blade B and the backing plate Bb are held unstably due to the breakage of the acute-angular tip portion K1 and the position of the cutting edge is deflected to the direction departing from the log W. This prevents a veneer being peeled off in a substantially uniform thickness.
This drawback may be solved by replacing the blade stock K with its acute-angular tip portion K1 broken by new one. However, since the blade stock is large and heavy as mentioned above, replacement thereof requires much labor and time and is expensive. Accordingly, problems are caused in that operational efficiency of the veneer lathe per se is extremely impaired, which leads to extremely impaired production efficiency of a veneer, and that cost of the replacement is high.
Further, the drawback may be solved with a blade stock K made of a steel which is hardly broken. In this case, however, an acute-angular tip portion K1 thereof is likely to undergo plastic deformation or bending to result in uneven position of the cutting edge of the cutting blade B. This prevents a veneer from being peeled off in a substantially uniform thickness.